This invention relates generally to milling or cold-planing machines for milling concrete or asphalt pavements. More specifically, the invention relates to a vacuum system for removing the millings or cuttings cut by the milling machine from the roadway.
Roadway repair is often accomplished by overlaying the existing pavement (whether of concrete or asphalt composition) with a new layer (often called a leveling course) of concrete, asphalt or other surfacing materials. Without prior surface treatment, however, this method of repair generally results in the application of insufficient quantities of paving material in the rutted, potholed or otherwise damaged areas, because the overlayment will be applied at the same rate per unit of roadway width in damaged areas (which have a greater depth across the width) as in the undamaged areas. The resulting reduced density in the overlayment of the previously damaged areas will lead to renewed rutting or other wear damage in the new pavement in relatively short order. However, by milling or planing the surface of the damaged pavement to a flat surface, the damaged areas will be eliminated and the new pavement will have a uniform density across the entire width of the roadway. In addition, a repaying technique that includes milling a thickness of old pavement and replacing it with an equivalent thickness of new pavement will return the elevation of the roadway to its initial level, whereas the placement of a leveling course atop damaged pavement will tend to raise the surface of the roadway or some portion thereof above its original elevation. This can require the raising of road shoulders, guardrails and manhole covers and the adjustment of overpass clearances, all of which is unnecessary if a proper milling technique is employed. A use of milling prior to repaying can also permit ready establishment of the proper road grade and slope, and thereby avoid drainage and safety problems. Furthermore, milling typically provides a rough surface that readily accepts and bonds with the new asphalt or other pavement overlayment. Finally, milling can provide raw material that can be reclaimed for use in the production of asphalt paving materials.
Milling machines are typically wheeled or track-mounted vehicles that are provided with a rotating drum that includes a plurality of cutting teeth. The drum is mounted on the frame of the machine and adapted to be lowered into contact with the road surface and rotated about a horizontal axis so as to cut into the surface to a desired depth as the machine is advanced along the roadway. Power for rotation of the drum is usually provided by the drive engine for the machine. Such machines are designed to cut into the pavement surface to a depth of eight inches (20.32 cm) or more, and for a width of up to 13 feet (3.96 m).
Generally, the milling machine also includes a conveyor system that is designed to carry the milled material that has been cut from the roadway by the rotating drum to a location in front of, to the rear of or beside the machine for deposit into a truck for removal from the site. This system generally uses the rotation of the milling drum and the proximity of the drum to the inlet of the conveyor to facilitate removal of most of the cuttings. However, such systems will not remove all such cuttings, and all or nearly all of such cuttings must be removed before new asphalt can be laid down. Consequently, a separate sweeper, vacuum truck or similar device is generally employed to remove the cuttings left behind by the milling machine. U.S. Pat. No. 4,139,318 of Jakob et al. describes a milling machine to which a conventional sweeper is attached so that the sweeper follows behind to remove fine dust left behind by the material collection system of the milling machine.
Some attempts have been made to avoid the need for a separate sweeper or vacuum truck in the milling process. Thus, attempts have been made to increase the efficiency of the material collection system of the milling machine by modifying the elements of the conveyor system, changing the arrangement of the conveyor inlet and the milling drum or by modifying the rate of rotation of the drum. Some such modifications and improvements are described in U.S. Pat. No. 4,193,636 of Jakob and U.S. Pat. No. 4,723,867 of Wirtgen. It is also known to incorporate a sweeping apparatus into a milling machine. Thus, for example, U.S. Pat. No. 4,561,145 of Latham describes a material collection system of a milling machine that includes a collection pan with a pair of rotating brushes associated therewith. The brushes are mounted adjacent to and on either side of the mouth of the collection pan and adapted to rotate about vertical axes in opposite directions so as to sweep material into the pan. A vacuum hose connects one side of the collection pan to a ho per in which a vacuum fan is mounted. An exhaust hose connects the opposite side of the collection pan to the opposite side of the hopper, thereby creating a flow of air across the width of the hopper from the exhaust hose to the vacuum hose. A baffle and spray bar in the hopper direct the flow of entrained material from the vacuum hose through a spray of water so that such material falls through the bottom of the hopper and onto a conveyor and is not entrained in the exhaust air passing through the exhaust hose.
All of these previously known systems for collecting material cut from a roadway have various disadvantages. The collection of cuttings by rotation of the cutting drum so as to cast material onto a precisely located input end of the cuttings conveyor is not sufficient to collect substantially all of the cuttings, especially those of finer particle sizes, from the drum. Furthermore, the Latham device with its rotating brushes: located on either side of a collection pan would seem to limit the width of cut that such a collection device could effectively clean. Consequently, subsequent cleaning steps, requiring additional equipment and time, would be required in order to collect substantially all the cuttings from a milling drum of practical width. It would be desirable if a system could be provided that could collect the cuttings from a milling drum, including cuttings of finer particle sizes, as they are cut from the roadway. It would also be desirable to provide such a system that could collect the cuttings of finer particle sizes and direct them to be collected along with the larger sized materials that are cast onto a cuttings conveyor for removal from the roadway site. It would also be desirable to provide such a system that could be mounted on the milling machine itself
Among the advantages of the invention is that it obviates the requirement to employ a separate sweeper or vacuum truck in the milling process. Another advantage of the invention is that it provides a system for collection of cuttings cut by the milling drum but left behind by the conventional removal system of the milling machine and depositing such cuttings onto a conveyor of the milling machine for removal from the roadway site.
Additional objects and advantages of this invention will become apparent from an examination of the drawings and the ensuing description.
As used herein, the term xe2x80x9cvacuum pumpxe2x80x9d refers to a device that creates suction or a partial vacuum.
The invention is a vacuum system for a portable milling machine which includes a milling drum mounted on a frame for rotation about its axis in order to cut material from the surface in the path of the machine. The vacuum system includes a vacuum pump having an air inlet and an air outlet, and a nozzle mounted behind the milling drum. The nozzle has an opening which is adapted to receive material cut from the surface by the drum. The vacuum system also includes a material collector having an inlet, an air outlet and a material outlet. The collector is adapted for collecting material entrained in air by the pump through the collector inlet and for discharging such material through the material outlet onto a conveyor mounted on the milling machine. The vacuum system also includes a first conduit and a second conduit. The first conduit connects the nozzle and the inlet of the material collector, and the second conduit connects the air outlet of the material collector and the air inlet of the pump.